The present invention relates to field of data networks and specifically to systems and methods of improving network performance. Network proxies and other types of network devices can be used to cache or store network data, accelerate network traffic, or otherwise control or affect network traffic between clients and servers.
As used herein, “client” generally refers to a computer, computing device, peripheral, electronics, or the like, that makes a request for data or an action, while “server” generally refers to a computer, computing device, peripheral, electronics, or the like, that operates in response to requests for data or action made by one or more clients. A computer or other device may be considered a client, a server, or both depending upon the context of its behavior.
As used herein, a request can be for operation of the computer, computing device, peripheral, electronics, or the like, and/or for an application being executed or controlled by the client. One example is a computer running a word processing program that needs a document stored externally to the computer and uses a network file system client to make a request over a network to a file server. Another example is a request for an action directed at a server that itself performs the action, such as a print server, a processing server, a database server, a control server, and equipment interface server, an I/O (input/output) server, etc.
A request is often satisfied by a response message supplying the data requested or performing the action requested, or a response message indicating an inability to service the request, such as an error message or an alert to a monitoring system of a failed or improper request. A server might also block a request, forward a request, transform a request, or the like, and then respond to the request or not respond to the request. Generally, a request-response cycle can be referred to as a “transaction” and for a given transaction, some object (physical, logical and/or virtual) can be said to be the “client” for that transaction and some other object (physical, logical and/or virtual) can be said to be the “server” for that transaction.
A client issues request messages to a server, which typically delivers a response message to each request message back to the client. As described in McCanne I and McCanne IV, a network proxy communicating with one or more peer network proxies can provide transaction acceleration, traffic reduction, and other functions over a wide area network interposed between two local area networks (LANs). Typically, in such a configuration, a client's request is intercepted by a client-side network proxy, which is connected with the client via a client LAN, and delivered via the WAN to a server-side network proxy. The server-side network proxy delivers the client request message to the server via a server LAN. The request message may be transformed or processed by the two proxies so that the request message (and possibly future request messages) are more effectively transported across the intervening network than would be true without the use of the cooperating network proxies. A message generally can be structured in any format or data structure suitable for conveying information over a communications network, including a single network packet or multiple network packets.
In these proxy-based systems, packets sent from the client are received at the client-side proxy; packets from the client-side proxy are received at the server-side proxy; and packets from the server-side proxy are received at the server. In many networks, these arrangements from client to server are sufficient to ensure the reverse direction of communication from server to client as well, viz. that packets from the server are received at the server-side proxy, packets from the server-side proxy are received at the client-side proxy, and packets from the client-side proxy are received at the client.
However, in some network environments this reverse direction of communication is more problematic. In particular, a LAN including a client or server can have multiple redundant connections with the WAN. As a result, asymmetric routing can produce situations in which a response packet from server to client may traverse a different path than the path used by a request packet from client to server. Where the proxies can rearrange the communication between client and server without the knowledge or participation of the client or server, reverse traffic that bypasses the proxies and their hidden cooperative arrangements can cause performance degradation or a total failure of the proxied connection between client and server. This problem with network proxies and asymmetric routing is mentioned in “Transparent Proxy Signalling,” Knutsson, Bjorn and Peterson, Larry, Journal of Communications Networks, March 2001; however, no solution to this problem is proposed.
It is therefore desirable for a system and method to override the effects described here. It is further desirable for the system and method to redirect related sequences of network traffic through the appropriate WAN or other network connection. It is additionally desirable for the system and method to remain transparent to clients and servers while redirecting network traffic through the appropriate WAN or other network connection.